Holliday called out the company for its "appalling" marketing tactic and Instagram for not regulating its sponsored content.

Model Tess Holliday unexpectedly came across a photo of herself being used in an Instagram advertisement and what she saw infuriated her.

The plus-size model, who is known for being an outspoken leader of the body positivity movement, recently discovered that a photo editing app called PIP CAM had used one of her pictures without her permission. In the ad, Holliday's body (along with the bodies of other plus-size women) is digitally altered to appear much slimmer.

Given that the 32-year-old constantly preaches the importance of self-acceptance and loving your body as it is, she was obviously upset when she saw that her image being used in an ad that directly contradicts her personal beliefs. Holliday took to Instagram to call out the company directly.

"An app that has nearly 50k downloads was dumb enough to steal photos of myself and two other plus-size women and use them for this nonsense. I'm sharing this because I wanna address a few things," Holliday wrote in Wednesday's post.

The model first slammed this type of marketing, calling it "appalling" that anyone think it's okay. Then Holliday moved on to rail against Instagram itself for failing to appropriately regulate its sponsored content.

"In a world of paid content, flat tummy teas, appetite suppressing lollipops (so many), it's important for me to tell y'all that I have [not] and will never partner with a brand or do paid content unless I genuinely use it or would recommend it to my best friend," she explained. "I've been offered crazy amounts of money to sell y'all all kinds of things like teeth whitening (that doesn't work), weight loss products (that are dangerous), etc., but that's me — to each their own."

Holliday ended her post with an empowering reminder for her followers and a warning for the app that stole her photo.

"Lastly, never let anyone make you feel like you need to alter your appearance or who you are. You are enough. You are worthy of love in your current body, whatever that body looks like," the mom of two wrote. "As for this bogus app, my lawyers will be sliding in your DM's boo."

People reached out to Instagram and the makers of PIP CAM for comment, but they've yet to respond.